Cluster-wide service agents

ABSTRACT

One or more techniques and/or systems are provided for cluster configuration information replication, managing cluster-wide service agents, and/or for cluster-wide outage detection. In an example of cluster configuration information replication, a replication workflow corresponding to a storage operation implemented for a storage object (e.g., renaming of a volume) of a first cluster may be transferred to a second storage cluster for selectively implementation. In an example of managing cluster-wide service agents, cluster-wide service agents are deployed to nodes of a cluster storage environment, where a master agent actively processes cluster service calls and standby agents passively wait for reassignment as a failover master in the event the master agent fails. In an example of cluster-wide outage detection, a cluster-wide outage may be determined for a cluster storage environment based upon a number of inaccessible nodes satisfying a cluster outage detection metric.

RELATED APPLICATIONS

This application claims priority to and is a continuation of U.S.application Ser. No. 15/368,609, filed on Dec. 4, 2016, titled“CLUSTER-WIDE SERVICE AGENTS,” which claims priority to and is acontinuation of U.S. Pat. No. 9,514,010, filed on Sep. 19, 2014, titled“CLUSTER-WIDE SERVICE AGENTS,” which are incorporated herein byreference.

BACKGROUND

A cluster storage environment may comprise one or more storage clusters.A storage cluster may comprise one or more nodes. A node may beconfigured to provide client devices with access to user data stored onstorage devices. Nodes may be configured according to various policies,such as a high availability policy where two nodes are paired togethersuch that a primary node actively services client I/O requests and asecondary node passively waits to provide failover recovery operation onbehalf of the primary node in the event the primary node experiences afailure. Various issues, such as an inability for clients to access userdata, may arise when information is not reliably replicated betweennodes and/or storage clusters, when cluster-wide outages are notdetected, and/or when failover operation is not implemented in anefficient manner.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a component block diagram illustrating an example clusterednetwork in accordance with one or more of the provisions set forthherein.

FIG. 2 is a component block diagram illustrating an example data storagesystem in accordance with one or more of the provisions set forthherein.

FIG. 3 is a flow chart illustrating an exemplary method of clusterconfiguration information replication.

FIG. 4A is a component block diagram illustrating an exemplary systemfor cluster configuration information replication using a firstreplication workflow.

FIG. 4B is a component block diagram illustrating an exemplary systemfor cluster configuration information replication using a secondreplication workflow.

FIG. 4C is a component block diagram illustrating an exemplary systemfor cluster configuration information replication using a thirdreplication workflow.

FIG. 4D is a component block diagram illustrating an exemplary systemfor cluster configuration information replication using a fourthreplication workflow.

FIG. 5 is a flow chart illustrating an exemplary method of clusterconfiguration information replication.

FIG. 6 is a flow chart illustrating an exemplary method of managingcluster-wide service agents.

FIG. 7A is a component block diagram illustrating an exemplary systemfor managing cluster-wide service agents, where one or more cluster-wideservice agents are deployed.

FIG. 7B is a component block diagram illustrating an exemplary systemfor managing cluster-wide service agents, where cluster-wide serviceagents are assigned as either master agents or standby agents.

FIG. 7C is a component block diagram illustrating an exemplary systemfor managing cluster-wide service agents, where a master agent fails.

FIG. 7D is a component block diagram illustrating an exemplary systemfor managing cluster-wide service agents, where a cluster-wide serviceagent is reassigned as a failover master.

FIG. 8 is a flow chart illustrating an exemplary method of cluster-wideoutage detection.

FIG. 9A is a component block diagram illustrating an exemplary systemfor cluster-wide outage detection.

FIG. 9B is a component block diagram illustrating an exemplary systemfor cluster-wide outage detection, where a service level outage isdetected.

FIG. 9C is a component block diagram illustrating an exemplary systemfor cluster-wide outage detection, where a cluster-wide outage isdetected.

FIG. 10 is an example of a computer readable medium in accordance withone or more of the provisions set forth herein.

DETAILED DESCRIPTION

Some examples of the claimed subject matter are now described withreference to the drawings, where like reference numerals are generallyused to refer to like elements throughout. In the following description,for purposes of explanation, numerous specific details are set forth inorder to provide an understanding of the claimed subject matter. It maybe evident, however, that the claimed subject matter may be practicedwithout these specific details. Nothing in this detailed description isadmitted as prior art.

One or more systems and/or techniques for cluster configurationinformation replication, for managing cluster-wide service agents,and/or for cluster-wide outage detection are provided herein.

In an example of cluster configuration information replication, acluster configuration schema may be defined for storage objects, of afirst storage cluster, that are to be actively monitored to changesresulting from storage operations (e.g., a name change operation for afirst volume; a resize operation, but not a name change operation, for asecond volume; a modification to a storage policy; etc.). Responsive todetermining that a storage operation was implemented for a storageobject as defined by the cluster configuration schema, a replicationworkflow may be created for the storage object based upon a change tothe storage object by the storage operation (e.g., a new name for thefirst volume). The replication workflow may comprise storage clusterconfiguration data that may be used by a second storage cluster toimplement the replication workflow for replication of the storageoperation from the first storage cluster to the second storage cluster(e.g., a name of a replicated first volume, corresponding to areplication of the first volume, at the second storage cluster may bechanged based upon the new name of the first volume). Because merelythose storage objects and storage operations that are defined by thecluster configuration schema are evaluated for replication, theefficiency of cluster configuration information replication may beimproved (e.g., as opposed to blindly replicating all storage objectsand storage operations) to increase speed, conserve memory, reduceprocessor load, reduce network bandwidth, etc. The second storagecluster may selectively implement the replication workflow and/or maytransform some the replication workflow (e.g., a prefix may be appendedto the new name before being applied to the replicated volume).

In an example of managing cluster-wide service agents, cluster-wideservice agents are deployed to nodes within a cluster storageenvironment. A cluster-wide service agent may be assigned as a masteragent that is configured to actively process cluster service calls(e.g., API calls to a set of storage cluster services, such as areplication cluster service, a storage policy cluster service, a volumecreation cluster service, etc.). The remaining cluster-wide serviceagents may be assigned as standby agents that may be configured topassively wait for reassignment as failover master agent (e.g., areassignment from being a standby agent to being a new master agent dueto a failure of a previous master agent). Because less than allcluster-wide service agents are designated as the master agent (e.g.,merely a single cluster-wide service agent), a single interface pointmay be provided for accessing cluster services, which may mitigateprocessing and memory resources otherwise designated for load balancing.Because a standby agent may be quickly reassigned as a failover masterin the event a master agent fails (e.g., a master agent crashes or isresponding below an acceptable latency threshold), high availability ofcluster services is provided.

In an example of cluster-wide outage detection, a cluster outagedetection metric for a cluster storage environment, comprising pluralityof nodes, may be defined. For example, the cluster outage detectionmetric may specify that a cluster-wide outage occurs when a majority ofnodes are inaccessible, otherwise merely a service level outage of aservice or application may have occurred. In this way, operationalinformation of the plurality nodes may be evaluated to determine whetherthe cluster outage detection metric is satisfied, and thus acluster-wide outage is determined for the cluster storage environment.Various decisions may be made based upon the cluster-wide outage, suchas whether a primary virtual server is to be retained in a down state oris to be brought online. In this way, appropriate actions may be takenin the event of a cluster-wide outage (e.g., a synchronization actionwith a failover cluster that provide failover operation during thecluster-wide outage, a recovery action, a policy change action, etc.) sothat the cluster storage environment may become operational and/orstabilized efficiently and/or sooner so that users may regain access touser data and/or cluster services.

To provide context for cluster configuration information replication,managing cluster-wide service agents, and/or cluster-wide outagedetection, FIG. 1 illustrates an embodiment of a clustered networkenvironment (e.g., a clustered storage environment, a storage cluster,etc.) or a network storage environment 100. It may be appreciated,however, that the techniques, etc. described herein may be implementedwithin the clustered network environment 100, a non-cluster networkenvironment, and/or a variety of other computing environments, such as adesktop computing environment. That is, the instant disclosure,including the scope of the appended claims, is not meant to be limitedto the examples provided herein. It will be appreciated that where thesame or similar components, elements, features, items, modules, etc. areillustrated in later figures but were previously discussed with regardto prior figures, that a similar (e.g., redundant) discussion of thesame may be omitted when describing the subsequent figures (e.g., forpurposes of simplicity and ease of understanding).

FIG. 1 is a block diagram illustrating an example clustered networkenvironment 100 (e.g., a clustered storage environment, a storagecluster, etc.) that may implement at least some embodiments of thetechniques and/or systems described herein. The example environment 100comprises data storage systems or storage sites 102 and 104 that arecoupled over a cluster fabric 106, such as a computing network embodiedas a private Infiniband or Fibre Channel (FC) network facilitatingcommunication between the storage systems 102 and 104 (and one or moremodules, component, etc. therein, such as, nodes 116 and 118, forexample). It will be appreciated that while two data storage systems 102and 104 and two nodes 116 and 118 are illustrated in FIG. 1, that anysuitable number of such components is contemplated. In an example, nodes116, 118 comprise storage controllers (e.g., node 116 may comprise aprimary or local storage controller and node 118 may comprise asecondary or remote storage controller) that provide client devices,such as host devices 108, 110, with access to data stored within datastorage devices 128, 130. Similarly, unless specifically providedotherwise herein, the same is true for other modules, elements,features, items, etc. referenced herein and/or illustrated in theaccompanying drawings. That is, a particular number of components,modules, elements, features, items, etc. disclosed herein is not meantto be interpreted in a limiting manner.

It will be further appreciated that clustered networks are not limitedto any particular geographic areas and can be clustered locally and/orremotely. Thus, in one embodiment a clustered network can be distributedover a plurality of storage systems and/or nodes located in a pluralityof geographic locations; while in another embodiment a clustered networkcan include data storage systems (e.g., 102, 104) residing in a samegeographic location (e.g., in a single onsite rack of data storagedevices).

In the illustrated example, one or more host devices 108, 110 which maycomprise, for example, client devices, personal computers (PCs),computing devices used for storage (e.g., storage servers), and othercomputers or peripheral devices (e.g., printers), are coupled to therespective data storage systems 102, 104 by storage network connections112, 114. Network connection may comprise a local area network (LAN) orwide area network (WAN), for example, that utilizes Network AttachedStorage (NAS) protocols, such as a Common Internet File System (CIFS)protocol or a Network File System (NFS) protocol to exchange datapackets. Illustratively, the host devices 108, 110 may begeneral-purpose computers running applications, and may interact withthe data storage systems 102, 104 using a client/server model forexchange of information. That is, the host device may request data fromthe data storage system (e.g., data on a storage device managed by anetwork storage control configured to process I/O commands issued by thehost device for the storage device), and the data storage system mayreturn results of the request to the host device via one or more networkconnections 112, 114.

The nodes 116, 118 on clustered data storage systems 102, 104 cancomprise network or host nodes that are interconnected as a cluster toprovide data storage and management services, such as to an enterprisehaving remote locations, for example. Such a node in a data storage andmanagement network cluster environment 100 can be a device attached tothe network as a connection point, redistribution point or communicationendpoint, for example. A node may be capable of sending, receiving,and/or forwarding information over a network communications channel, andcould comprise any device that meets any or all of these criteria. Oneexample of a node may be a data storage and management server attachedto a network, where the server can comprise a general purpose computeror a computing device particularly configured to operate as a server ina data storage and management system.

In an example, a first cluster of nodes such as the nodes 116, 118(e.g., a first set of storage controllers configured to provide accessto a first storage aggregate comprising a first logical grouping of oneor more storage devices) may be located on a first storage site. Asecond cluster of nodes, not illustrated, may be located at a secondstorage site (e.g., a second set of storage controllers configured toprovide access to a second storage aggregate comprising a second logicalgrouping of one or more storage devices). The first cluster of nodes andthe second cluster of nodes may be configured according to a disasterrecovery configuration where a surviving cluster of nodes providesswitchover access to storage devices of a disaster cluster of nodes inthe event a disaster occurs at a disaster storage site comprising thedisaster cluster of nodes (e.g., the first cluster of nodes providesclient devices with switchover data access to storage devices of thesecond storage aggregate in the event a disaster occurs at the secondstorage site).

As illustrated in the exemplary environment 100, nodes 116, 118 cancomprise various functional components that coordinate to providedistributed storage architecture for the cluster. For example, the nodescan comprise a network module 120, 122 (e.g., N-Module, or N-Blade) anda data module 124, 126 (e.g., D-Module, or D-Blade). Network modules120, 122 can be configured to allow the nodes 116, 118 (e.g., networkstorage controllers) to connect with host devices 108, 110 over thenetwork connections 112, 114, for example, allowing the host devices108, 110 to access data stored in the distributed storage system.Further, the network modules 120, 122 can provide connections with oneor more other components through the cluster fabric 106. For example, inFIG. 1, a first network module 120 of first node 116 can access a seconddata storage device 130 by sending a request through a second datamodule 126 of a second node 118.

Data modules 124, 126 can be configured to connect one or more datastorage devices 128, 130, such as disks or arrays of disks, flashmemory, or some other form of data storage, to the nodes 116, 118. Thenodes 116, 118 can be interconnected by the cluster fabric 106, forexample, allowing respective nodes in the cluster to access data on datastorage devices 128, 130 connected to different nodes in the cluster.Often, data modules 124, 126 communicate with the data storage devices128, 130 according to a storage area network (SAN) protocol, such asSmall Computer System Interface (SCSI) or Fiber Channel Protocol (FCP),for example. Thus, as seen from an operating system on a node 116, 118,the data storage devices 128, 130 can appear as locally attached to theoperating system. In this manner, different nodes 116, 118, etc. mayaccess data blocks through the operating system, rather than expresslyrequesting abstract files.

It should be appreciated that, while the example embodiment 100illustrates an equal number of N and D modules, other embodiments maycomprise a differing number of these modules. For example, there may bea plurality of N and/or D modules interconnected in a cluster that doesnot have a one-to-one correspondence between the N and D modules. Thatis, different nodes can have a different number of N and D modules, andthe same node can have a different number of N modules than D modules.

Further, a host device 108, 110 can be networked with the nodes 116, 118in the cluster, over the networking connections 112, 114. As an example,respective host devices 108, 110 that are networked to a cluster mayrequest services (e.g., exchanging of information in the form of datapackets) of a node 116, 118 in the cluster, and the node 116, 118 canreturn results of the requested services to the host devices 108, 110.In one embodiment, the host devices 108, 110 can exchange informationwith the network modules 120, 122 residing in the nodes (e.g., networkhosts) 116, 118 in the data storage systems 102, 104.

In one embodiment, the data storage devices 128, 130 comprise volumes132, which is an implementation of storage of information onto diskdrives or disk arrays or other storage (e.g., flash) as a file-systemfor data, for example. Volumes can span a portion of a disk, acollection of disks, or portions of disks, for example, and typicallydefine an overall logical arrangement of file storage on disk space inthe storage system. In one embodiment a volume can comprise stored dataas one or more files that reside in a hierarchical directory structurewithin the volume.

Volumes are typically configured in formats that may be associated withparticular storage systems, and respective volume formats typicallycomprise features that provide functionality to the volumes, such asproviding an ability for volumes to form clusters. For example, where afirst storage system may utilize a first format for their volumes, asecond storage system may utilize a second format for their volumes.

In the example environment 100, the host devices 108, 110 can utilizethe data storage systems 102, 104 to store and retrieve data from thevolumes 132. In this embodiment, for example, the host device 108 cansend data packets to the N-module 120 in the node 116 within datastorage system 102. The node 116 can forward the data to the datastorage device 128 using the D-module 124, where the data storage device128 comprises volume 132A. In this way, in this example, the host devicecan access the storage volume 132A, to store and/or retrieve data, usingthe data storage system 102 connected by the network connection 112.Further, in this embodiment, the host device 110 can exchange data withthe N-module 122 in the host 118 within the data storage system 104(e.g., which may be remote from the data storage system 102). The host118 can forward the data to the data storage device 130 using theD-module 126, thereby accessing volume 1328 associated with the datastorage device 130.

It may be appreciated that cluster configuration informationreplication, managing cluster-wide service agents, and/or cluster-wideoutage detection may be implemented within the clustered networkenvironment 100 (e.g., a clustered storage environment, a storagecluster, etc.). For example, a replication component, an agentmanagement component, and/or an outage detection component may beimplemented for the node 116 and/or the node 118. In this way, clusterconfiguration data may be replicated between the node 116, the node 118,and/or other nodes of storage clusters not illustrated; cluster-wideservice agents may be deployed on the node 116 and/or the node 118;and/or a cluster-wide outage may be determined based uponinaccessibility of the node 116 and/or the node 118.

FIG. 2 is an illustrative example of a data storage system 200 (e.g.,102, 104 in FIG. 1), providing further detail of an embodiment ofcomponents that may implement one or more of the techniques and/orsystems described herein. The example data storage system 200 comprisesa node 202 (e.g., host nodes 116, 118 in FIG. 1), and a data storagedevice 234 (e.g., data storage devices 128, 130 in FIG. 1). The node 202may be a general purpose computer, for example, or some other computingdevice particularly configured to operate as a storage server. A hostdevice 205 (e.g., 108, 110 in FIG. 1) can be connected to the node 202over a network 216, for example, to provides access to files and/orother data stored on the data storage device 234. In an example, thenode 202 comprises a storage controller that provides client devices,such as the host device 205, with access to data stored within datastorage device 234.

The data storage device 234 can comprise mass storage devices, such asdisks 224, 226, 228 of a disk array 218, 220, 222. It will beappreciated that the techniques and systems, described herein, are notlimited by the example embodiment. For example, disks 224, 226, 228 maycomprise any type of mass storage devices, including but not limited tomagnetic disk drives, flash memory, and any other similar media adaptedto store information, including, for example, data (D) and/or parity (P)information.

The node 202 comprises one or more processors 204, a memory 206, anetwork adapter 210, a cluster access adapter 212, and a storage adapter214 interconnected by a system bus 242. The storage system 200 alsoincludes an operating system 208 installed in the memory 206 of the node202 that can, for example, implement a Redundant Array of Independent(or Inexpensive) Disks (RAID) optimization technique to optimize areconstruction process of data of a failed disk in an array.

The operating system 208 can also manage communications for the datastorage system, and communications between other data storage systemsthat may be in a clustered network, such as attached to a cluster fabric215 (e.g., 106 in FIG. 1). Thus, the node 202, such as a network storagecontroller, can respond to host device requests to manage data on thedata storage device 234 (e.g., or additional clustered devices) inaccordance with these host device requests. The operating system 208 canoften establish one or more file systems on the data storage system 200,where a file system can include software code and data structures thatimplement a persistent hierarchical namespace of files and directories,for example. As an example, when a new data storage device (not shown)is added to a clustered network system, the operating system 208 isinformed where, in an existing directory tree, new files associated withthe new data storage device are to be stored. This is often referred toas “mounting” a file system.

In the example data storage system 200, memory 206 can include storagelocations that are addressable by the processors 204 and adapters 210,212, 214 for storing related software program code and data structures.The processors 204 and adapters 210, 212, 214 may, for example, includeprocessing elements and/or logic circuitry configured to execute thesoftware code and manipulate the data structures. The operating system208, portions of which are typically resident in the memory 206 andexecuted by the processing elements, functionally organizes the storagesystem by, among other things, invoking storage operations in support ofa file service implemented by the storage system. It will be apparent tothose skilled in the art that other processing and memory mechanisms,including various computer readable media, may be used for storingand/or executing program instructions pertaining to the techniquesdescribed herein. For example, the operating system can also utilize oneor more control files (not shown) to aid in the provisioning of virtualmachines.

The network adapter 210 includes the mechanical, electrical andsignaling circuitry needed to connect the data storage system 200 to ahost device 205 over a computer network 216, which may comprise, amongother things, a point-to-point connection or a shared medium, such as alocal area network. The host device 205 (e.g., 108, 110 of FIG. 1) maybe a general-purpose computer configured to execute applications. Asdescribed above, the host device 205 may interact with the data storagesystem 200 in accordance with a client/host model of informationdelivery.

The storage adapter 214 cooperates with the operating system 208executing on the node 202 to access information requested by the hostdevice 205 (e.g., access data on a storage device managed by a networkstorage controller). The information may be stored on any type ofattached array of writeable media such as magnetic disk drives, flashmemory, and/or any other similar media adapted to store information. Inthe example data storage system 200, the information can be stored indata blocks on the disks 224, 226, 228. The storage adapter 214 caninclude input/output (I/O) interface circuitry that couples to the disksover an I/O interconnect arrangement, such as a storage area network(SAN) protocol (e.g., Small Computer System Interface (SCSI), iSCSI,hyperSCSI, Fiber Channel Protocol (FCP)). The information is retrievedby the storage adapter 214 and, if necessary, processed by the one ormore processors 204 (or the storage adapter 214 itself) prior to beingforwarded over the system bus 242 to the network adapter 210 (and/or thecluster access adapter 212 if sending to another node in the cluster)where the information is formatted into a data packet and returned tothe host device 205 over the network connection 216 (and/or returned toanother node attached to the cluster over the cluster fabric 215).

In one embodiment, storage of information on arrays 218, 220, 222 can beimplemented as one or more storage “volumes” 230, 232 that are comprisedof a cluster of disks 224, 226, 228 defining an overall logicalarrangement of disk space. The disks 224, 226, 228 that comprise one ormore volumes are typically organized as one or more groups of RAIDs. Asan example, volume 230 comprises an aggregate of disk arrays 218 and220, which comprise the cluster of disks 224 and 226.

In one embodiment, to facilitate access to disks 224, 226, 228, theoperating system 208 may implement a file system (e.g., write anywherefile system) that logically organizes the information as a hierarchicalstructure of directories and files on the disks. In this embodiment,respective files may be implemented as a set of disk blocks configuredto store information, whereas directories may be implemented asspecially formatted files in which information about other files anddirectories are stored.

Whatever the underlying physical configuration within this data storagesystem 200, data can be stored as files within physical and/or virtualvolumes, which can be associated with respective volume identifiers,such as file system identifiers (FSIDs), which can be 32-bits in lengthin one example.

A physical volume corresponds to at least a portion of physical storagedevices whose address, addressable space, location, etc. doesn't change,such as at least some of one or more data storage devices 234 (e.g., aRedundant Array of Independent (or Inexpensive) Disks (RAID system)).Typically the location of the physical volume doesn't change in that the(range of) address(es) used to access it generally remains constant.

A virtual volume, in contrast, is stored over an aggregate of disparateportions of different physical storage devices. The virtual volume maybe a collection of different available portions of different physicalstorage device locations, such as some available space from each of thedisks 224, 226, and/or 228. It will be appreciated that since a virtualvolume is not “tied” to any one particular storage device, a virtualvolume can be said to include a layer of abstraction or virtualization,which allows it to be resized and/or flexible in some regards.

Further, a virtual volume can include one or more logical unit numbers(LUNs) 238, directories 236, qtrees 235, and files 240. Among otherthings, these features, but more particularly LUNS, allow the disparatememory locations within which data is stored to be identified, forexample, and grouped as data storage unit. As such, the LUNs 238 may becharacterized as constituting a virtual disk or drive upon which datawithin the virtual volume is stored within the aggregate. For example,LUNs are often referred to as virtual drives, such that they emulate ahard drive from a general purpose computer, while they actually comprisedata blocks stored in various parts of a volume.

In one embodiment, one or more data storage devices 234 can have one ormore physical ports, wherein each physical port can be assigned a targetaddress (e.g., SCSI target address). To represent respective volumesstored on a data storage device, a target address on the data storagedevice can be used to identify one or more LUNs 238. Thus, for example,when the node 202 connects to a volume 230, 232 through the storageadapter 214, a connection between the node 202 and the one or more LUNs238 underlying the volume is created.

In one embodiment, respective target addresses can identify multipleLUNs, such that a target address can represent multiple volumes. The I/Ointerface, which can be implemented as circuitry and/or software in thestorage adapter 214 or as executable code residing in memory 206 andexecuted by the processors 204, for example, can connect to volume 230by using one or more addresses that identify the LUNs 238.

It may be appreciated that cluster configuration informationreplication, managing cluster-wide service agents, and/or cluster-wideoutage detection may be implemented for the data storage system 200(e.g., a data storage system within a clustered storage environment, astorage cluster, etc.). For example, a replication component, an agentmanagement component, and/or an outage detection component may beimplemented for the 202. In this way, cluster configuration data may bereplicated between the node 202 and/or other nodes of storage clustersnot illustrated; a cluster-wide service agent may be deployed on thenode 202; and/or a cluster-wide outage may be determined based uponinaccessibility of the node 202 and/or other nodes not illustrated.

One embodiment of cluster configuration information replication isillustrated by an exemplary method 300 of FIG. 3. A cluster storageenvironment may comprise one or more storage clusters. A storage clustermay comprise a plurality of nodes (e.g., storage controllers) thatmanage storage (e.g., provide clients with access to user data;implement backup policies; allocate new storage volumes; etc.), whichmay involve user data (e.g., a text file stored by a client on a storagedevice) and cluster configuration information (e.g., a size of a storageobject, a name of a storage object, a location or directory comprising astorage object, a path used to access user data, a replication policy, abackup policy, an IP address of a storage object, a junction path, aninternal configuration of a storage controller, etc.). A storage objectmay comprise a LUN, a volume, a vserver, a snapshot policy, a storageaggregate, and/or other cluster configuration information.

A cluster configuration schema may define semantics of storage objectsand/or storage operations of a first storage cluster, such that areplication component and/or a second storage cluster may use thecluster configuration schema to gain an understanding about thesemantics of cluster configuration information of the first storagecluster. For example, the second storage cluster may use the semanticsto perform a transformation upon volume cluster configurationinformation of a volume that is being replicated from the first storagecluster to the second storage cluster (e.g., the second storage clustermay apply a new name, a new IP address, and a new storage directory toreplicated volume cluster configuration information that may be relevantto the second storage cluster, as opposed to using names, IP address,and/or storage directory information that may otherwise be relevant tomerely the first storage cluster).

The cluster configuration scheme may comprise a hierarchical collectionof storage objects and storage operations (e.g., storage operations thatare available to perform upon the storage objects, which will result ina change to the cluster configuration information of the first storagecluster). The cluster configuration schema may specify a set of objectcharacteristics and/or a set of storage operations that are to becaptured for inclusion within a replication workflow that is to bereplicated from the first storage cluster to the second storage cluster(e.g., a name change for a LUN (C); a resize operation for a volume (A);a write operation to a volume (B); etc.). Object characteristics,storage operations, and/or storage objects that are not specified by thecluster configuration schema may be disqualified for inclusion withinthe replication workflow (e.g., a write operation to the volume (A); abackup operation for a LUN (D); etc.). In this way, merely objectcharacteristics, storage operations, and/or storage objects specified bythe cluster configuration schema may be replicated.

At 302, the method starts. At 304, the cluster configuration schema maybe evaluated to identify a first storage object, of the first storagecluster, that is to be actively monitored for change (e.g., a changeresulting in a change of cluster configuration information) resultingfrom a first storage operation. For example, the volume (A) may bemonitored for a change resulting from a resize operation. At 306,responsive to determining that the first storage operation wasimplemented for the first storage object, a replication workflow for thefirst storage object may be generated based upon a change to the firststorage object by the first storage operation (e.g., the volume (A) maybe resized based upon the resize operation). The replication workflowmay comprise the first storage operation (e.g., a description of theresize operation), an input for the first storage operation (e.g., atarget new size for the volume (A)), and a result of the first storageoperation (e.g., a resulting new size for the volume (A)). In an examplewhere volume (A) was previously replicated from the first storagecluster to the second storage cluster as a replicated volume (A), thereplication workflow may comprise an update workflow for the replicatedvolume (A). In an example where the replication workflow is associatedwith a set of storage objects, the replication workflow may comprise abaseline workflow for the set of storage objects (e.g., an initialbaseline replication of volume (A), volume (B), volume (C), LUN (A), LUN(B), LUN (C), and/or other storage objects that are to be initiallyreplicated/baselined to the second storage cluster, such that subsequentchanges to the storage objects may be updated through update workflows).

In an example, a second storage operation that was implemented for asecond storage object may be identified (e.g., a storage controller (C)may be reconfigured). Responsive to the cluster configuration scheme notdefining the second storage object as being actively monitored forchange by the second storage operation, the second storage operation maybe disqualified for inclusion within the replication workflow (e.g., thestorage controller (C) may not be monitored for reconfigurationchanges). In an example, a third storage operation that was implementedfor a first storage object may be identified (e.g., a write operation tothe volume (A)). Responsive to the cluster configuration scheme notdefining the first storage object as being actively monitored for changeby the third storage operation, the third storage operation may bedisqualified for inclusion within the replication workflow (e.g., thevolume (A) may be monitored for resizing but not for write operations).

In an example, the cluster configuration schema may define a replicationdomain as comprising the first storage object and a fourth storageobject. Responsive to determining that a fourth storage operation wasimplemented for the fourth storage object, the fourth storage operationmay be included within the replication workflow. A storage operationreplay order may be defined for the first storage operation and thefourth storage operation. The storage operation replay order may beincluded within the replication workflow so that the second storagecluster may maintain a desired replication replay order when replayingstorage operations from the replication workflow.

At 308, the replication workflow may be transferred to the secondstorage cluster for selective implementation of the replicationworkflow. In an example, the monitoring of the first storage object, thegeneration of the replication workflow, the transfer of the replicationworkflow, and/or the selective implementation of the replicationworkflow may be performed in real-time so that the second storagecluster may be kept up-to-date with respect to the first storagecluster. In an example, a transformation upon the replication workflowmay be facilitated to modify a characteristic of the first storageoperation to create a transformed replication workflow for selectiveimplementation by the second storage cluster. The transformation maycomprise a volume name change, a volume size change, an IP addresschange, a name change, a destination location change, a policy change, ajunction path change, a storage object property change, and/or any othercluster configuration information change. For example, the secondstorage cluster may transform the resize storage operation to target areplicated volume (A) IP address of the replicated volume (A) of thesecond storage cluster, as opposed to an IP address of the volume (A).In another example, the resize storage operation may be transformed totarget a replicated volume (A) name, of the replicate volume (A), thatmay be different than a volume (A) name of the volume (A) of the firststorage cluster.

In an example, the replication workflow may comprise a set of storageinformation associated with a set of storage objects (e.g., the volume(A), a volume (F), a LUN (F), etc.) and/or a set of storage operations(e.g., the resize operation for the volume (A), a write operation to thevolume (F), a backup operation for the LUN (F), etc.). A selectiveimplementation of a first portion of the set of storage information, butnot a second portion of the set of storage information, by the secondstorage cluster may be facilitated. For example, the second storagecluster may have an interest in the volume (A) and the volume (F), butnot the LUN (F).

In an example, a disaster associated with the first storage cluster maybe identified. Responsive to the disaster, the second storage clustermay be invoked to operate according to a disaster recovery mode in placeof the first storage cluster based upon the selective implementation ofthe replication workflow (e.g., the second storage cluster may provideclients with access to replicated user data stored by the second storagecluster). A switchback replication workflow may be generated based uponthe second storage cluster operating according to the disaster recoverymode (e.g., a client may modify a name of the volume (A) and may performvarious write operations to a volume (G)). The switchback replicationworkflow may be transferred to the first storage cluster for switchbackoperation from the second storage cluster to the first storage clusterupon disaster recovery of the first storage cluster (e.g., oncerecovered, the first storage cluster may be synchronized using theswitchback replication workflow so that the first storage cluster maycomprise up-to-date information resulting for operations performed bythe second storage cluster while in the disaster recovery mode. In thisway, cluster configuration information may be selectively replicatedand/or transformed between the first storage cluster and the secondstorage cluster. At 310, the method ends.

FIGS. 4A-4D illustrate examples of a system 401, comprising areplication component 408, for cluster configuration informationreplication. FIG. 4A illustrates an example 400 of the replicationcomponent 408 being associated with a first storage cluster 402 and asecond storage cluster 414 (e.g., the replication component 408 may behosted on a first node within the first storage cluster 402, hosted on asecond node within the second storage cluster 414, or hosted on a remotenode that is not within the first storage cluster 402 or the secondstorage cluster 414). The replication component 408 may maintain acluster configuration schema 410 defining storage objects and/or storageoperations that are to be monitored for changes that result in clusterconfiguration information changes. For example, the clusterconfiguration schema 410 may specify that a first storage object 406(e.g., a snapshot policy) is to be monitored for change resulting from afirst storage operation 404 (e.g., a snapshot interval change for thesnapshot policy).

Responsive to determining that the first storage operation 404 wasimplemented for the first storage object 406, a replication workflow 412may be generated for the first storage object 406 based upon a change tothe first storage object 406 by the first storage operation 404. Thereplication workflow 412 may comprise the first storage operation 404(e.g., the snapshot interval change), an input for the first storageoperation 404 (e.g., a snapshot interval increase amount), and a resultof the first storage operation 404 (e.g., a new snapshot interval). Thereplication workflow 412 may be transferred to the second storagecluster 414 for selective implementation 416 by the second storagecluster 414. For example, the second storage cluster 414 may determinewhen and how to implement 416 the replication workflow 412 (e.g., a timeat which to perform the first storage operation 404 upon a replicatedsnapshot policy maintained by the second storage cluster 414; thesnapshot interval increase amount may be transformed, such as decreased,to create a transformed snapshot interval increase amount that is to beused for implementing 416 the replication workflow 412 upon thereplicated snapshot policy; etc.).

FIG. 4B illustrates an example 430 of the replication component 408generating a second replication workflow 436. For example, the clusterconfiguration schema 410 may specify that a second storage object 434(e.g., a storage aggregate for which the snapshot policy may beenforced) is to be monitored for change by a second storage operation432 (e.g., a rename storage aggregate operation for the storageaggregate). Responsive to the first storage operation 404 beingperformed on the first storage object 406 and the second storageoperation 432 being performed on the second storage object 434, thereplication component 408 may generate the second replication workflow436 for the first storage operation 404 and the second storage operation432. The replication component 408 may define a storage operation replayorder 438 for the first storage operation 404 and the second storageoperation 432 (e.g., the name of the storage aggregate may be changedbefore the snapshot policy is modified so that a new name of the storageaggregate can be applied to the modified snapshot policy). The storageoperation replay order 438 may be included in the second replicationworkflow 436, and the second replication workflow 436 may be transferredfor the second storage cluster 414 for implementation 440 according tothe storage operation replay order 438. For example, the second storageoperation 432 may be applied to a replicated storage aggregate of thesecond storage cluster 414, and then the first storage operation 404 maybe applied to the replicated backup policy of the second storage cluster414. In an example where the second storage cluster 414 transforms thesecond replication workflow 436, the second storage cluster maytransform the second storage operation 432 by appending a prefix to thenew name that is to be applied to the replicated storage aggregate.

FIG. 4C illustrates an example 450 of the replication component 408generating a third replication workflow 462. The cluster configurationschema 410 may not identify a third storage object 454 for monitoringfor changes by a third storage operation 452. Responsive to the firststorage operation 404 being performed on the first storage object 406,the second storage operation 432 being performed on the second storageobject 434, and the third storage operation 452 being performed on thethird storage object 454, the replication component 408 may generate thethird replication workflow 462 for the first storage operation 404 andthe second storage operation 452 but not the third storage operation 452(e.g., the replication component 408 may disqualify the third storageoperation 452 based upon the cluster configuration schema 410). Forexample, the replication component 408 may include a first storageobject change 456 of the first storage object 406 by the first storageoperation 404 and a second storage object change 458 of the secondstorage object 434 by the second storage operation 432 in the thirdreplication workflow 462. The third replication workflow 462 may betransferred to the second storage cluster 414 for selectiveimplementation 460 of the first storage object change 456 and/or thesecond storage object change 458 (e.g., the second storage cluster 414may merely implement to second storage object change 458 but not thefirst storage object change 456).

FIG. 4D illustrates an example 480 of the second storage cluster 414implementing 488 a transformed replication workflow. For example, thecluster configuration schema 410 may specify that a fourth storageoperation 482 (e.g., a create new volume operation) is to be monitored.Responsive to the fourth storage operation 482 being performed to createa fourth storage object 484 (e.g., a new volume having a volume namecharacteristic “Test Volume”, a directory characteristic “/temp”, and/orother characteristics), the replication component 408 may generate afourth replication workflow 486 for the fourth storage operation 482.The replication component 408 may transfer the fourth replicationworkflow 486 to the second storage cluster 414 for implementation 488.The second storage cluster 414 may transform the fourth replicationworkflow 486 to create the transformed replication workflow. Forexample, the volume name characteristic “Test Volume” may be transformedto a transformed volume name characteristic “Testing 123” and thedirectory characteristic “/temp” may be transformed to a transformeddirectory characteristic “/working” for inclusion within the transformedreplication workflow. In this way, the transformed replication workflowmay be implemented by the second storage controller 414.

One embodiment of cluster configuration information replication isillustrated by an exemplary method 500 of FIG. 5. At 504, a clusterconfiguration schema may be specified, such as by a second storagecluster that is to receive replicated cluster configuration informationfrom a first storage cluster in the form of replication workflows. Thecluster configuration schema may define storage objects, of the firststorage cluster, that are to be actively monitored for change resultingfrom storage operations (e.g., a first storage object that is to beactively monitored for change resulting from a first storage operation,such as a volume that is to be monitored for resize operations, renameoperations, etc.). At 506, the second storage cluster may receive areplication workflow indicating that the first storage operation wasimplemented for the first storage object (e.g., the volume may have beenresized to a new size and renamed to a new name). In an example, thereplication workflow may comprise a set of storage information, such asa first portion corresponding to the new size resulting from the resizeoperation and a second portion corresponding to the new name resultingfrom the renaming operation. At 508, the first portion of thereplication workflow may be selectively implemented on the secondstorage cluster. For example, the resize operation may be implementedfor a replicated volume of the second storage cluster. In an example,the second storage cluster may selectively not implement the secondportion by disqualifying the new name due to the new name violating anaming policy of the second storage cluster. In this way, portions ofstorage information, within the replication workflow, may be selectivelyimplemented or disqualified by the second storage controller. At 510,the method ends.

One embodiment of managing cluster-wide service agents is illustrated byan exemplary method 600 of FIG. 6. A cluster storage environment maycomprise a plurality of nodes (e.g., storage controllers) that managestorage (e.g., provide clients with access to user data stored on avolume), which may involve user data (e.g., a text file stored by aclient on a storage device) and cluster configuration information (e.g.,a size, name, and location of the volume). Cluster-wide service agentsmay be deployed to respective nodes within the cluster storageenvironment (e.g., one cluster-wide service agent per node). In anexample, a master policy may be enforced for the cluster-wide serviceagents (e.g., a single master policy specifying that merely 1cluster-wide service agent is to be a master agent at any given time; amaster policy specifying that less than all cluster-wide service agentsare to be a master agent at any given time; etc.). A cluster-wideservice agent that is assigned as a master agent may be configured toactively process cluster service calls (e.g., API calls for a set ofstorage cluster services, such as a backup cluster service, areplication cluster service, a policy cluster service, a volume creationcluster service, etc., managed by the master agent).

At 604, a first cluster-wide service agent may be deployed to a firstnode within the cluster storage environment. At 606, a secondcluster-wide service agent may be deployed to a second node within thecluster storage environment. In an example, the first cluster-wideservice agent may comprise a first physical process configured toactively process API calls for the set of storage cluster services whilehaving a master agent assignment. The second cluster-wide service agentmay comprise a second physical process (e.g., a second instance of thefirst physical process) configured to actively process API calls for theset of storage cluster services while having the master agentassignment.

At 608, the first cluster-wide service agent may be assigned as themaster agent configured to actively process cluster service calls. In anexample, a first set of operational statistics for the firstcluster-wide service agent (e.g., historical response time to API calls,historical downtime of unavailability, etc.) may be evaluated against asecond set of operational statistics for the second cluster-wide serviceagent to award a cluster-wide service agent, such as the firstcluster-wide service agent, as the master agent (e.g., the secondcluster-wide service agent may have historically slow response times forservicing API calls in comparison with the first cluster-wide serviceagent). Because the master agent may experience a failure at some point,a sync point may be defined for the master agent so that the masteragent synchronizes cluster service call processing information that maybe used by a cluster-wide service agent that may takeover for the masteragent as a failover master agent. In an example, a storage clusterservice data cache may be maintained for use by the master agent. Afirst IP address of the first cluster-wide service agent, as the masteragent, may be assigned to the storage cluster service data cache. Inthis way, the master agent may store/cache cluster service callprocessing data within the storage cluster service data cache.

At 610, the second cluster-wide service agent may be assigned as astandby agent configured to passively wait for reassignment as afailover master agent (e.g., the failover master agent may be a masteragent that takes over for a failed master agent). In an example, aninterface may be exposed to the first cluster-wide service agent and/orthe second cluster-wide service agent. The interface may comprise aninitialization interface, a shutdown interface, an acquire master dutiesinterface, a release master duties interface, etc. The interface may beexposed according to an asynchronous and/or idempotent implementation.In this way, the first cluster-wide service agent and/or the secondcluster-wide service agent may perform various functionality using theinterface (e.g., the first cluster-wide service agent may release masterduties using the release master duties interface).

A failure of the master agent may be detected. In an example, the firstnode may fail. In another example, the first cluster-wide service agentmay not be responding or providing a heartbeat. In another example, thefailure may be identified based upon a first set of operationalstatistics for the first cluster-wide service agent indicating that thefirst cluster-wide service agent is not satisfying a performancecriteria (e.g., a relatively slow response time for servicing clusterservice calls). At 612, responsive to the failure, the firstcluster-wide service agent may be reassigned as the standby agent. At614, the second cluster-wide service agent may be reassigned as thefailover master agent configured to actively process cluster servicecalls based upon the failure. In an example, the second cluster-wideservice agent may be automatically assigned as the failover master agentin real-time based upon a service interruption tolerance metric in orderto mitigate service interruption of cluster service calls.

In an example, the storage cluster service data cache may be purged toremove the first IP address from the storage cluster service data cache.A second IP address of the second cluster-wide service agent may beassigned to the storage cluster service data cache. The service clusterservice data cache may be maintained for use by the second cluster-wideservice agent as the failover master agent. In an example, inter processremote procedure calls may be retargeted to the failover master agentbased upon the assignment of the second IP address to the storagecluster service data cache so that the second cluster-wide service agentcan process cluster service calls as the failover master agent. Interprocess remote procedure calls may be retargeted according to anoriginal network configuration of the cluster storage environment beforethe failure of the master agent (e.g., the second cluster-wide serviceagent can start processing cluster service calls without changing anetwork configuration of the cluster storage environment). In anexample, the second cluster-wide service agent, as the failover masteragent, may be instructed to perform a clean-up of prior cluster servicecall processing that was in progress by the first cluster-wide serviceagent before the failure. In this way, cluster-wide service agents maybe managed for the cluster storage environment. At 616, the method ends.

FIGS. 7A-7D illustrate examples of a system 701, comprising an agentmanagement component 702, for managing cluster-wide service agents. FIG.7A illustrates an example 700 of the agent management component 702being associated with a cluster storage environment 704 comprising afirst node 706, a second node 708, a third node 710, and/or other nodesnot illustrated. The agent management component 702 may deploy 720cluster-wide service agents to such nodes, such as a first cluster-wideservice agent 712 to the first node 706 (e.g., a first physical processexecuting on the first node 706), a second cluster-wide service agent714 to the second node 708 (e.g., a second physical process executing onthe second node 708), a third cluster-wide service agent 716 to thethird node 710 (e.g., a third physical process executing on the thirdnode 710), etc. The agent management component 702 may maintain astorage cluster service data cache 718 that may be used by a masteragent for processing cluster service calls (e.g., API calls to a policycluster service, a backup cluster service, a volume creation clusterservice, etc.).

FIG. 7B illustrates an example 730 of the agent management component 702assigning 732 cluster-wide service agents as either standby agents ormaster agents. It may be appreciated that any number or percentage ofcluster-wide service agents may be assigned as master agents, and thatassigning a single cluster-wide service agent as a master agent ismerely an example (e.g., having a single master agent may mitigateresource usage and/or complexity that may otherwise have been devoted toload balancing between multiple master agents, while still providinghigh availability of cluster service access through the single masteragent because a standby agent may be reassigned as a failover masteragent in real-time to mitigate downtime of client access to clusterservices). In an example, the first cluster-wide service agent 712 maybe assigned as a first standby agent 734, the second cluster-wideservice agent 714 may be assigned as a second standby agent 738, and thethird cluster-wide service agent 716 may be assigned as a master agent736. A standby agent may be configured to passively wait forreassignment as a failover master agent. The master agent 736 may beconfigured to actively process cluster service calls. A thirdcluster-wide service agent IP address, of the third cluster-wide serviceagent 716, may be assigned to the storage cluster service data cache 718so that the third cluster-wide service agent 716 may utilize the storagecluster service data cache 718 for processing cluster service calls.

FIG. 7C illustrates an example 740 of the agent management component 702detecting 744 a failure 742 of the master agent 736. For example, thethird node 710 may crash, resulting in the failure 742 of the thirdcluster-wide service agent 716 as the master agent 736. The agentmanagement component 702 may purge 746 the storage cluster service datacache to remove the third cluster-wide service agent IP address 748based upon the failure 742 of the master agent 736, resulting in apurged storage cluster service data cache 718 a that may be ready foruse by a failover master agent.

FIG. 7D illustrates an example 750 of the agent management component 702performing a reassignment 752 based upon the failure 742 (e.g., example740 of FIG. 7C). For example, the agent management component 702 mayassign the third cluster-wide service agent 716 as a third standby agent756 (e.g., during and/or after the failure 742). The agent managementcomponent 702 may evaluate a first set of operational statistics for thefirst cluster-wide service agent 712 (e.g., historical response times tocluster service calls, historical downtime or unavailability,operational characteristics of the first node 706, available resourcesof the first node 706, etc.) against a second set of operationalstatistics for the second cluster-wide service agent 714 (e.g.,historical response times to cluster service calls, historical downtimeor unavailability, operational characteristics of the second node 708,available resources of the second node 708, etc.) to determine whichcluster-wide service agent should be awarded as a failover master. Forexample, the second cluster-wide service agent 714 may have desiredoperational statistics compared to the first cluster-wide service agent712, and thus the second cluster-wide service agent 714 may be awardedas a failover master 754 configured to actively process cluster servicecalls. In an example, the reassignment 752 of the second cluster-wideservice agent 714 from the second standby agent 738 to the failovermaster 754 may be performed in real-time based upon a serviceinterruption tolerance metric to mitigate service interruption ofcluster service calls (e.g., a zero or close to zero tolerance forinterruptions in processing cluster service calls). A secondcluster-wide service agent IP address 758 of the second cluster-wideservice agent 714 may be assigned to the purged storage cluster servicedata cache 718 a, resulting in a restored storage cluster service datacache 718 b that may be used by the failover master 754 to activelyprocess cluster service calls.

One embodiment of cluster-wide outage detection is illustrated by anexemplary method 800 of FIG. 8. A storage cluster environment maycomprise a plurality of nodes (e.g., storage controllers) configured tomanage storage, such as by providing clients with access to user datastored on storage devices and/or by implementing various storagepolicies (e.g., a backup policy, a caching policy, etc.). At 804, acluster outage detection metric may be defined for the cluster storageenvironment. In an example, the cluster outage detection metric mayspecify that a cluster-wide outage occurs when a majority of nodes areinaccessible. It may be appreciated that the cluster outage detectionmetric may specify a variety of criteria and/or situations that may bedeemed as a cluster-wide outage resulting in the storage clusterenvironment becoming inaccessible (e.g., a threshold percentage ofinaccessible nodes; a number of concurrently rebooting nodes; etc.).

At 806, the plurality of nodes may be evaluated to identify a number ofinaccessible nodes (e.g., a node that may not be currently capable ofprocessing cluster service calls and/or performing storage functionalitysuch as providing clients with access to user data of the clusterstorage environment) within the cluster storage environment. In anexample, a node may be identified as inaccessible based upon a powercycle of the cluster storage environment. In another example, a node maybe identified as inaccessible based upon a halt and reboot sequence ofthe node. In another example, a node may be identified as inaccessiblebased upon a kernel panic of the node. In another example, a node may beidentified as inaccessible based upon a failure resulting in a halt ofthe node. In an example, cluster reboot detection may be performed toidentify inaccessible nodes during a node reboot sequence after anoutage. For example, the node reboot sequence may correspond to a numberof nodes exceeding the cluster outage detection metric (e.g., a majorityof nodes) concurrently rebooting.

At 808, responsive to the number of inaccessible nodes satisfying thecluster outage detection metric (e.g., a majority of nodes may beinaccessible), a cluster-wide outage may be determined for the clusterstorage environment. In an example, a node reboot, indicative of acluster level outage, may be distinguished from a service reboot and/oran application reboot that are indicative of a service level outage. Thecluster level outage may be indicative of inaccessibility of the clusterstorage environment, whereas the service level outage may merelycorrespond to inaccessibility of one or more nodes that results in aloss of access to an application or service provided by such nodes(e.g., inaccessibility to a backup policy service, a migration service,a volume creation service, a LUN renaming service, a storageapplication, etc.). In an example, node quorum logic for the clusterstorage environment may be used to determine the cluster-wide outage. Afirst cluster-wide outage entry may be stored in a cluster storagestructure (e.g., a database). A sequence number (e.g., a uniqueidentifier for the cluster-wide outage) may be assigned to the firstcluster-wide outage entry. The sequence number may be different thansequence numbers assigned to other cluster-wide outage entries (e.g.,uniquely identifying other previously identified cluster-wide outages)within the cluster storage structure. In an example, a cluster outageduration for the cluster-wide outage may be specified, such as withinthe first cluster-wide outage entry. Various decisions may be made basedupon the cluster-wide outage. For example, a determination as whether toretain a primary virtual server in a down state or bring the primaryvirtual server into an online state may be made based upon thecluster-wide outage. At 810, the method ends.

FIGS. 9A-9C illustrate examples of a system 910, comprising an outagedetection component 902, for cluster-wide outage detection. FIG. 9Aillustrates an example 900 of the outage detection component 902 beingassociated with a cluster storage environment 906. The cluster storageenvironment 906 may comprise a first node 908, a second node 910, athird node 912, a fourth node 914, a fifth node 916, a sixth node 918, aseventh node 920, and/or other nodes not illustrated. The outagedetection component 902 may define a cluster outage detection metric 904for the cluster storage environment 906. The cluster outage detectionmetric 904 may specify that a cluster-wide outage (e.g., inaccessibilityof the cluster storage environment 906) occurs for the cluster storageenvironment 906 when a threshold percentage of nodes (e.g., a majorityof nodes) are inaccessible (e.g., not responding, rebooting, failed,halted, etc.), otherwise merely a service level outage may be detected(e.g., an inaccessibility of one or more nodes that results in a loss ofaccess to an application or service provided by such nodes). In anexample, no cluster-wide outage may be detected because a number ofinaccessible nodes does not satisfy the cluster outage detection metric,such as because the first node 908 is operational 922, the second node910 is operation 924, the third node 912 is operational 926, the fourthnode 914 is operational 928, the fifth node 916 is operational 930, thesixth node 918 is operational 932, and the seventh node 920 isoperational 934.

FIG. 9B illustrates an example 940 of the outage detection component 902identifying a service level outage 948 associated with the clusterstorage environment 906. For example, the outage detection component 902may determine that the third node 912 has become inaccessible 942, thefourth node 914 has become inaccessible 944, and the fifth node 916 hasbecome inaccessible 946. The outage detection component 902 maydetermine that the inaccessibility of the third node 912, the fourthnode 914, and the fifth node 916 does not satisfy the cluster outagedetection metric 904 (e.g., less than a majority of nodes may beinaccessible). Instead, the outage detection component 902 may identifythe service level outage 948 (e.g., an inaccessibility for clients toaccess a cluster service and/or an application hosted by the third node912, the fourth node 914, and the fifth node 916).

FIG. 9C illustrates an example 950 of the outage detection component 902identifying a cluster-wide outage 964. For example, the outage detectioncomponent 902 may determine that the first node 908 has becomeinaccessible 952, the second node 910 has become inaccessible 954, thethird node 912 has become inaccessible 956, the fourth node 914 hasbecome inaccessible 958, the fifth node 916 has become inaccessible 960,and the sixth node 918 has become inaccessible 962. The outage detectioncomponent 902 may determine that the inaccessibility of the first node908, the second node 910, the third node 912, the fourth node 914, thefifth node 916, and the sixth node 918 satisfies the cluster outagedetection metric 904 (e.g., more than a majority of nodes may beinaccessible), and thus the outage detection component 902 may identifythe cluster-wide outage 964 (e.g., the cluster storage environment 906may be inaccessible due to the outage notwithstanding the operationalstate 934 of the seventh node 920). Various decisions may be made basedupon the cluster-wide outage (e.g., whether to retain a primary virtualserver in a down state or bring the primary virtual server into anonline state; whether to implement a cluster restoration operation;whether to synchronize cluster configuration data of the cluster storageenvironment 906 with a failover cluster storage environment thatprovided failover operation on behalf of the cluster storage environment906 during the failure).

Still another embodiment involves a computer-readable medium comprisingprocessor-executable instructions configured to implement one or more ofthe techniques presented herein. An example embodiment of acomputer-readable medium or a computer-readable device that is devisedin these ways is illustrated in FIG. 10, wherein the implementation 1000comprises a computer-readable medium 1008, such as a CD-ft DVD-R, flashdrive, a platter of a hard disk drive, etc., on which is encodedcomputer-readable data 1006. This computer-readable data 1006, such asbinary data comprising at least one of a zero or a one, in turncomprises a set of computer instructions 1004 configured to operateaccording to one or more of the principles set forth herein. In someembodiments, the processor-executable computer instructions 1004 areconfigured to perform a method 1002, such as at least some of theexemplary method 300 of FIG. 3, at least some of the exemplary method500 of FIG. 5, at least some of the exemplary method 600 of FIG. 6,and/or at least some of the exemplary method 800 of FIG. 8, for example.In some embodiments, the processor-executable instructions 1004 areconfigured to implement a system, such as at least some of the exemplarysystem 401 of FIGS. 4A-4D, at least some of the exemplary system 701 ofFIGS. 7A-7D, and/or at least some of the exemplary system 901 of FIGS.9A-9C, for example. Many such computer-readable media are contemplatedto operate in accordance with the techniques presented herein.

It will be appreciated that processes, architectures and/or proceduresdescribed herein can be implemented in hardware, firmware and/orsoftware. It will also be appreciated that the provisions set forthherein may apply to any type of special-purpose computer (e.g., filehost, storage server and/or storage serving appliance) and/orgeneral-purpose computer, including a standalone computer or portionthereof, embodied as or including a storage system. Moreover, theteachings herein can be configured to a variety of storage systemarchitectures including, but not limited to, a network-attached storageenvironment and/or a storage area network and disk assembly directlyattached to a client or host computer. Storage system should thereforebe taken broadly to include such arrangements in addition to anysubsystems configured to perform a storage function and associated withother equipment or systems.

In some embodiments, methods described and/or illustrated in thisdisclosure may be realized in whole or in part on computer-readablemedia. Computer readable media can include processor-executableinstructions configured to implement one or more of the methodspresented herein, and may include any mechanism for storing this datathat can be thereafter read by a computer system. Examples of computerreadable media include (hard) drives (e.g., accessible via networkattached storage (NAS)), Storage Area Networks (SAN), volatile andnon-volatile memory, such as read-only memory (ROM), random-accessmemory (RAM), EEPROM and/or flash memory, CD-ROMs, CD-Rs, CD-RWs, DVDs,cassettes, magnetic tape, magnetic disk storage, optical or non-opticaldata storage devices and/or any other medium which can be used to storedata.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter defined in the appended claims is not necessarilylimited to the specific features or acts described above. Rather, thespecific features and acts described above are disclosed as exampleforms of implementing at least some of the claims.

Various operations of embodiments are provided herein. The order inwhich some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated given the benefit ofthis description. Further, it will be understood that not all operationsare necessarily present in each embodiment provided herein. Also, itwill be understood that not all operations are necessary in someembodiments.

Furthermore, the claimed subject matter is implemented as a method,apparatus, or article of manufacture using standard programming orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer program accessible from anycomputer-readable device, carrier, or media. Of course, manymodifications may be made to this configuration without departing fromthe scope or spirit of the claimed subject matter.

As used in this application, the terms “component”, “module,” “system”,“interface”, and the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware, software, or software in execution. For example, a componentincludes a process running on a processor, a processor, an object, anexecutable, a thread of execution, a program, or a computer. By way ofillustration, both an application running on a controller and thecontroller can be a component. One or more components residing within aprocess or thread of execution and a component may be localized on onecomputer or distributed between two or more computers.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication are generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Also, at least one of A and B and/or the like generally means A orB and/or both A and B. Furthermore, to the extent that “includes”,“having”, “has”, “with”, or variants thereof are used, such terms areintended to be inclusive in a manner similar to the term “comprising”.

Many modifications may be made to the instant disclosure withoutdeparting from the scope or spirit of the claimed subject matter. Unlessspecified otherwise, “first,” “second,” or the like are not intended toimply a temporal aspect, a spatial aspect, an ordering, etc. Rather,such terms are merely used as identifiers, names, etc. for features,elements, items, etc. For example, a first set of information and asecond set of information generally correspond to set of information Aand set of information B or two different or two identical sets ofinformation or the same set of information.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method, comprising: assigning a first agent,deployed to a first node, as a master agent configured to activelyprocess cluster service API calls and a second agent, deployed to asecond node, as a standby agent; maintaining a storage cluster servicedata cache for use by the master agent, wherein the master agent storesservice call processing data within the storage cluster service datacache; and assigning a first network address of the first agent to thestorage cluster service data cache based upon the first agent being themaster agent.
 2. The method of claim 1, comprising: purging the storagecluster service data cache to replace the first network address with asecond network address of the second agent based upon the second agentbeing reassigned as the master agent in place of the first agent.
 3. Themethod of claim 2, comprising: retargeting an inter process remoteprocedure call to the second agent based upon the assignment of thesecond network address to the storage cluster service data cache.
 4. Themethod of claim 1, comprising: directing inter process remote procedurecalls to the first agent based upon the first network address beingassigned to the storage cluster service data cache.
 5. The method ofclaim 1, comprising: reassigning the second agent as the master agentbased upon a service interruption tolerance metric associated withservice interruption of the cluster service API calls.
 6. The method ofclaim 1, comprising: reassigning the second agent as the master agentbased upon operational statistics of the second agent exceedingoperational statistics of the first agent.
 7. The method of claim 1,comprising: enforcing a single master policy for the first agent and thesecond agent.
 8. The method of claim 1, comprising: evaluating a firstset of operational statistics for the first agent against a second setof operational statistics for the second agent to award the first agentas the master agent.
 9. A computing device, comprising: a memory havingstored thereon instructions for performing a method; and a processorcoupled with the memory, the processor configured to execute theinstructions to cause the processor to: assign a first agent, deployedto a first node, as a master agent configured to actively processcluster service API calls and a second agent, deployed to a second node,as a standby agent; maintain a storage cluster service data cache foruse by the master agent, wherein the master agent stores service callprocessing data within the storage cluster service data cache; andassign a first network address of the first agent to the storage clusterservice data cache based upon the first agent being the master agent.10. The computing device of claim 9, wherein the instructions cause theprocessor to: purge the storage cluster service data cache to replacethe first network address with a second network address of the secondagent based upon the second agent being reassigned as the master agentin place of the first agent.
 11. The computing device of claim 10,wherein the instructions cause the processor to: retarget an interprocess remote procedure call to the second agent based upon assignmentof the second network address to the storage cluster service data cache.12. The computing device of claim 9, wherein the instructions cause theprocessor to: direct inter process remote procedure calls to the firstagent based upon the first network address being assigned to the storagecluster service data cache.
 13. The computing device of claim 9, whereinthe instructions cause the processor to: reassign the second agent asthe master agent based upon a service interruption tolerance metricassociated with service interruption of the cluster service API calls.14. The computing device of claim 9, wherein the instructions cause theprocessor to: reassign the second agent as the master agent based uponoperational statistics of the second agent exceeding operationalstatistics of the first agent.
 15. The computing device of claim 9,wherein the instructions cause the processor to: enforce a single masterpolicy for the first agent and the second agent.
 16. The computingdevice of claim 9, wherein the instructions cause the processor to:evaluate a first set of operational statistics for the first agentagainst a second set of operational statistics for the second agent toaward the first agent as the master agent.
 17. A non-transitory computerreadable medium comprising instructions that, when executed by aprocessor, cause the processor to: assign a first agent, deployed to afirst node, as a master agent configured to actively process clusterservice API calls and a second agent, deployed to a second node, as astandby agent; maintain a storage cluster service data cache for use bythe master agent, wherein the master agent stores service callprocessing data within the storage cluster service data cache; andassign a first network address of the first agent to the storage clusterservice data cache based upon the first agent being the master agent.18. The non-transitory computer readable medium of claim 17, wherein theinstructions cause the processor to: purge the storage cluster servicedata cache to replace the first network address with a second networkaddress of the second agent based upon the second agent being reassignedas the master agent in place of the first agent.
 19. The non-transitorycomputer readable medium of claim 18, wherein the instructions cause theprocessor to: retarget an inter process remote procedure call to thesecond agent based upon assignment of the second network address to thestorage cluster service data cache.
 20. The non-transitory computerreadable medium of claim 17, wherein the instructions cause theprocessor to: direct inter process remote procedure calls to the firstagent based upon the first network address being assigned to the storagecluster service data cache.